State of the California Current 2019–2020: Back to the Future With Marine Heatwaves?

Abstract

The California Current System (CCS) has experienced large fluctuations in environmental conditions in recent years that have dramatically affected the biological community. Here we synthesize remotely sensed, hydrographic, and biological survey data from throughout the CCS in 2019–2020 to evaluate how recent changes in environmental conditions have affected community dynamics at multiple trophic levels. A marine heatwave formed in the north Pacific in 2019 and reached the second greatest area ever recorded by the end of summer 2020. However, high atmospheric pressure in early 2020 drove relatively strong Ekman-driven coastal upwelling in the northern portion of the CCS and warm temperature anomalies remained far offshore. Upwelling and cooler temperatures in the northern CCS created relatively productive conditions in which the biomass of lipid-rich copepod species increased, adult krill size increased, and several seabird species experienced positive reproductive success. Despite these conditions, the composition of the fish community in the northern CCS remained a mixture of both warm- and cool-water-associated species. In the southern CCS, ocean temperatures remained above average for the seventh consecutive year. Abundances of juvenile fish species associated with productive conditions were relatively low, and the ichthyoplankton community was dominated by a mixture of oceanic warm-water and cosmopolitan species. Seabird species associated with warm water also occurred at greater densities than cool-water species in the southern CCS. The population of northern anchovy, which has been resurgent since 2017, continued to provide an important forage base for piscivorous fishes, offshore colonies of seabirds, and marine mammals throughout the CCS. Coastal upwelling in the north, and a longer-term trend in warming in the south, appeared to be controlling the community to a much greater extent than the marine heatwave itself.

On the Seasonal Cycle of the Statistical Properties of Sea Surface Temperature

“…The seasonal variability of the upwelling front has been documented in previous studies (e.g., García-Reyes & Largier, 2012;Weber et al, 2021), so it could be foreseen that it was responsible for the seasonal variability of h ∞ . Nevertheless, the present research unveils additional results that emphasize the importance of upwellings in setting up some of the statistical properties of the flow.…”

Message in a Bottle: Archived DNA Reveals Marine Heatwave-Associated Shifts in Fish Assemblages

“…Although anchovy larvae abundance was low in spring during the 2014–2016 marine heatwave, anchovy recruitment was high in the summer of 2015 (Thompson, Schroeder, et al, 2019). Anchovy mature in approximately one to two years (Parrish et al, 1986; Sydeman et al, 2020), and thus the 2015 class likely began spawning in mid-2016 (Thompson et al, 2022a), leading to high anchovy spawning stock biomass and larval abundances by 2016 and lasting into at least 2021 (Thompson et al, 2022b; Weber et al, 2021).…”

Pacific bluefin tuna, Thunnus orientalis, exhibits a flexible feeding ecology in the Southern California Bight

“…During these warming events, the diets of multiple predators became dominated by anchovy (e.g. California sea lions ( Zalophus californianus ), rhinoceros auklet ( Cerorhinca monocerata ), [ 16 ]) and pelagic red crabs (yellowtail jack ( Seriola dorsalis , pers . communication and observation ), reflecting concerted food web changes across the CCS.…”